Laparoscopy is used in both diagnostic and surgical procedures. Currently, MIS procedures, as opposed to open surgical procedures, are routinely done in almost all hospitals. Minimally invasive techniques minimize trauma to the patient by eliminating the need to make large incisions. This both reduces the risk of infection and reduces the patient's hospital stay. Laparoscopic and endoscopic procedures in MIS use different types of endoscopes as imaging means, giving the surgeon an inside-the-body view of the surgical site. Specialized endoscopes are named depending on where they are intended to look. Examples include: cystoscope (bladder), nephroscope (kidney), bronchoscope (bronchi), laryngoscope (larynx+the voice box), otoscope (ear), arthroscope (joint), laparoscope (abdomen), gastrointestinal endoscopes, and specialized stereo endoscopes used as laparoscopes or for endoscopic cardiac surgery.
The endoscope may be inserted through a tiny surgical incision to view joints or organs in the chest or abdominal cavity. More often, the endoscope is inserted into a natural body orifice such as the nose, mouth, anus, bladder or vagina. There are three basic types of endoscopes: rigid, semi-rigid, and flexible. The rigid endoscope comes in a variety of diameters and lengths depending on the requirements of the procedure. Typical endoscopic procedures require a large amount of equipment. The main equipment used in conjunction to the visual part of the endoscopic surgery are the endoscope body, fiber optics illumination bundles, illumination light source, light source controller, imaging camera, camera control module, and video display unit.
The laparoscope is a rigid endoscope as illustrated in FIG. 1. It allows for visualization of the abdominopelvic cavities for diagnostic or surgical techniques. The laparoscope is inserted into the peritoneal cavity via a cannula that runs through the abdominal wall. There are many different features of laparoscopes, such as the size and field of vision, which determine the effectiveness of the instrument.
As illustrated in FIG. 1, the basic laparoscope is made up of a long thin tube 101 with an eyepiece 103 at one end for viewing into the patient. Fiber optic light introduced to the endoscope at fiber port 102, and launched into fiber optics 123 (FIG. 3) and 138 (FIG. 4), passes through the endoscope body 101, illuminating the area 124 that is being observed, as illustrated by radiation pattern 125 in FIG. 3. Laparoscopes are characterized by diameter and the direction of view. The direction of view is the angle 107 between the axis of the laparoscope 105 and the center field of view 106, as illustrated in FIG. 1. Typical endoscopes have lengths of approximately 30 cm and diameters in the range of 4 to 10 mm. Laparoscopes consist of two important lenses, the ocular lens at the eyepiece and the objective lens 122 at the distal end of the endoscope body 101 in FIG. 3. Other lens sets acting as relay lenses 121 in FIG. 3, are used in-between the objective lens and the eye piece or the CCD camera or image position 127. Imaging rays 126 traverse the length of the scope through all the imaging optics.
The rigid endoscope also comes in different viewing angles: 120 degree or retrograde, for viewing backward; 90 degree and 70 degree for lateral viewing; 30 degree (104 as illustrated in FIG. 1) and 45 degree for forward oblique views; and 0 degree for forward viewing. The angle of the objective lens 122 used is determined by the position of the structure to be viewed.
Other surgical instruments and tools are also inserted into the body, for the operation and specific surgical manipulation by the surgeon. The insertion is done through open tubes provided inside the endoscope body for instrument insertion, such as in gastrointestinal endoscopes, or through separate incisions in the abdominal or chest wall 113, using cannula 110 (straight or curved stainless steel or plastic tubes 101 which are inserted into a small opening or incision in the skin as illustrated in FIG. 2). The cannula opening 112a (receiving portion) at the proximal end 112 outside the body is used to receive and guide different instruments 300 inside the body, where they are exposed to the inside of the body at the distal end 111 (opening 111a) of the cannula 110 (FIG. 2). Cannulas can make a seal at the incision site 114.
In a typical gastrointestinal endoscope, a tool opening is provided at the distal end of the scope, where inserted medical instruments gain access to the body following the scope body.
Endoscopes can be diagnostic, for observation only, or operative, having channels for irrigation, suction, and the insertion of accessory instruments when a surgical procedure is planned. Thus, endoscope bodies also could provide mechanical or electrical control sections, buttons for valves such as a suction valve, a CO2 valve, a water bottle connector, a water feed, a suction port, etc. The common component that all endoscopes must be equipped with is a light guide section for illumination.
An illustration showing typical endoscope optics is shown in FIG. 3. Common imaging sections of the endoscope are an ocular or eyepiece, relay lenses 121 (in the case of rigid scopes), a flexible imaging fiber-optic bundle (in the case of flexible scopes), and an objective lens system 122. Endoscopes are either used as stand-alone units, with the surgeon looking into the scope from the ocular or eye piece of the endoscope, or in conjunction with digital cameras 127, where an image (rays 126) of the surgical site 124 is incident on the image capture device (charge coupled device or CCD) of the camera (127). Using a display device, the surgeon performs the operation looking at the image on the video monitor.
With recent technology improvements in the field of electronic imaging reducing the size of the image capture device (CCD), some endoscopes used in MIS and diagnostic procedures are equipped with a high resolution distal end camera system, commonly referred to as Chip on a Stick, one example of which is illustrated in FIG. 4. These flexible endoscopes use a CCD chip 137 at the distal end of the endoscope directly capturing the image through the objective lens 133, in which case the flexible part (132) of the endoscope body, contains only power (137a) and communication wires 137b for the CCD camera at the distal tip, rather than imaging optics 133 which is located in the rigid portion 131 of the endoscope. Light guides 138 are still necessary for this type of electronic scope to provide adequate lighting (134) of the surgical site 136 for imaging purposes.
Other, more complicated MIS systems make use of robotic surgical tools and instruments, and/or provide stereoscopic images of the surgical site for the surgeon, improving the surgeon's dexterity, precision and speed of operation. In these more sophisticated MIS imaging applications more specific types of illumination systems or multiple illuminators are used.
Endoscopes can have a variety of forms, ranging in diameter, tube length, and angle of view. However, all types of endoscopes commonly use optical fibers (123, and 138 in FIGS. 3 and 4) to illuminate the surgical site. Illumination is a very important part of laparoscopy because there is no light source inside the body. Fiber optic cold light is used to project light down the laparoscope from an external source. Large lamps with broadband output are used to couple light into the illumination light guides (123 and 138 in FIGS. 3 and 4), where light guides transfer the illumination light from the light source to the illumination fiber bundle (123, 138) inside the endoscope body 101. A typical scope attached to an illumination light guide (port 102) is shown in FIGS. 1, 3 and 4. One (FIG. 1) or more light guide bundles (FIGS. 3 and 4) are used to couple light into the endoscope illumination fiber bundles 123 and 138 of FIGS. 3 and 4.
The use of fiber bundles 123 and 138 inside the endoscope body 101 in FIG. 3 and FIG. 4, or tube 101 occupies substantial space that otherwise could have been used by the imaging optics. This can be seen in FIGS. 3 and 4, showing the fiber optic illuminators 123 and 138 sharing the endoscope body 101 with the imaging optics (121, 122, 133). Limitations on the optical lens terrain (121, 122, 133) diameter, as well as the imaging fiber bundle thickness, correlate directly to the imaging resolution vs. size of the image. The larger the lens diameter or imaging bundle thickness, the better the resolution of the endoscope for a certain field of view (FOV) or image size. This is the main reason that larger diameter scopes are considered better in optical quality than narrower scopes. However, large scope diameters are not desirable for certain operations where space is limited on the operation site.
Different illumination fiber geometries are used to reduce the space constraint inside the scope body. For this reason, and to have a more uniform illumination, the imaging fiber bundles are also split in some cases to have two or more points of illumination at the distal end of the scope. In other types of scopes, illumination is made into a circular ring pattern at least at the distal end of the endoscope, similar to the ring illumination of microscopy.
The light source for the endoscope is either a xenon bulb, which creates a high intensity white light suitable for smaller-diameter endoscopes, a halogen bulb, which creates a yellowish light suitable for general endoscopic work, or a Metal Halide lamp. Since most broadband light sources also produce large amounts of Infrared Red (IR) wavelength light, IR cut filters and lamp dichroic reflectors (heat blocking filters and reflectors that reduce the radiation usually associated with heat production) are used in the illumination light source to prevent the transfer of IR radiation to the body. Thus, broadband visible cold light is highly desirable in laparoscopic procedures providing decreased thermal injury to tissues. Since most CCD cameras are also sensitive to IR radiation (due to Silicon absorption spectrum), extra IR cut filters are used in front of the camera to prevent glare caused by IR radiation in the camera.
Despite the precautions used in reducing the IR radiation, in actuality some amount of infrared radiation in addition to the visible light enters the fiber optic cable, and is transmitted through the cable and scopes (port 102, fibers 123 and 138) into the body. When the light leaves the endoscope tip, the level of infrared radiation has usually been reduced to a safe level through absorption by the optical fibers in the endoscope, and substantial losses at the cable connections (port 102). However, if the cable is not connected to the endoscope, the infrared output is not reduced sufficiently and even could have the capability of igniting some materials if the cable is left at close proximity to absorbing combustible material. This hazard exists in fiber illumination cables with high intensity light sources.
Additionally, higher outputs not only increase the risk of fire, but may introduce the risk of burns during close-range inspection of tissue with the endoscopes. Absorption of high-intensity radiation at visible light wavelengths may also cause tissue heating, where additional filtering of infrared wavelengths may not eliminate this hazard. Furthermore, with the increasing use of television systems with video cameras connected to the endoscopes, many physicians operate light sources at their maximum intensities and believe they need even greater light intensities to compensate for inadequate illumination at peripheral areas of the image where the illumination intensity falls rather rapidly using today's standard illumination fiber guides.
Typical light sources are also deficient in their flux and color management of their spectral output. A typical lamp spectral output requires time to come to an acceptable level during the warm-up procedure, both in terms of lumens output as well as color quality or white point on the color gamut. The color temperature of the lamp based illuminators, are typically deficient in producing the desirable color temperature (daylight color temperature of 5600 Kelvin) for typical endoscopic procedure. Color content of the lamp output also typically shifts during the life time of the lamp. Thus it is usually required to perform a white color balance adjustment in the camera controller each time an endoscope is used subsequent to the light source warm-up procedure to obtain realistic color image. A repeat of the white color balance adjustment may also be necessary if the lamp intensity is adjusted through a large range.
Typical high power lamps also have very limited life time, measured in hours (Typically 50, 500, or 1000 hours for Halogen, Xenon or Metal Halide depending on the lamp), where the light output of the lamp degrades to about one half of its original light output. Typical lamp manufacturers typically do not specify or have a failure criteria based on the color quality for the lifetime of the lamp.
Complicated and bulky optical schemes are incorporated in the light guide optical sources for effective coupling of the light into the illumination fiber bundles (123 and 138). Special non-imaging optics such as glass rods, and lens elements are used to also uniformly couple light into all the fibers inside the illumination fiber bundle. All these increase the cost and also size of having high brightness, uniform fiber optic illumination light sources. Typical high brightness light sources also incorporate powerful fans to dissipate the large amount of heat generated inside the light source package. In fact in a typical endoscopic procedure, light sources are one of the main sources of heat generation and the associated fans on the light sources are one of the main sources of noise in the surgical environment. Large package size of high power lamps also add extra burden to the premium space in a diagnostic and surgical environment.
Light sources normally give off electromagnetic interference (EMI), where the starting pulses from the lamp could reset or otherwise interfere with other digital electronics devices in today's surgical environment.
In an operating environment, the light source(s) are placed at a distance, on a table top or rack, mounted away from the patient and the endoscope. Fiber optic light bundles to transfer the light from the light source to the endoscope are used as light links between the light source and the endoscope. These fiber bundles are not only bulky and expensive, but their price increases by the length of the fiber bundle, whereas the amount of light transmitted goes down as the length of the fiber bundle increases. To conveniently place the light source and fiber bundle away from the operational site, longer fiber bundles are necessary, however the attenuation, or drop in the transmitted optical flux increases with the length of the fiber used as well, requiring more powerful light sources.
Use of fiber optic light guides as a means of transfer of illumination light from the proximal 122 to the distal end 111 of the endoscope also increases the chance of relative light loss. The relative optical light-loss measurement quantifies the degree of light loss from the light source to the distal tip of the endoscope. The relative light loss will increase with fiber-optic (123, 138) damage. Extra heat will also be generated in the broken fiber ends inside the endoscope. In fact the major failure mode for the fiber optic bundles delivering the light to the endoscope, and the optical system inside the endoscope is breakage of the fibers.
As illustrated in FIGS. 1, 3 and 4, the illumination fiber bundle(s) port 102 commonly join the endoscope body at some angle near the ocular (103) at the proximal side 112 of the endoscope. The fiber guide body and the main endoscope body 101 are commonly joined together in a welding process at joint 108 illustrated in FIG. 1. The construction and design of this welded joint is often a weakness in the endoscope manufacturing and use, where after many operations, high temperature and high humidity sterilizations, and successive handling, this welded joint could get damaged and break, exposing the internal parts of the scope to the environment when the seal is broken.
Color CCD cameras use alternate color dies on the individual CCD pixels, to capture color images. Green and red, and green and blue pixels are alternated in rows. This spatial color sampling limits the color resolution of the color CCD cameras, since each pixel is dedicated to capturing a single color in the color image.
Three (3) chip CCD cameras (red CCD chip, blue CCD chip, and green CCD chip) are also used in high resolution applications, where all the pixels in each CCD are dedicated to detecting the single color content of the image. The individual color captured images from the 3 CCDs are then put together electronically, as the multi-color image is reproduced on the viewing display. Three chip CCD cameras are expensive and bulky.